Southern limit of Africanized honey bees in Argentina inferred by mtDNA and wing geometric morphometric analysis

African honey bee subspecies Apis mellifera scutellata began to spread in the American continent from southern Brazil in 1956. The process of Africanization involved both maternal and paternal bidirectional gene flow between European and Africanized honey bees. In Argentina, Africanized honey bees dominate in the northern semitropical regions and a hybrid area is defined between (ca. 32°–34°latitude). Although previous analysis has been carried out in Buenos Aires province, no analysis has been made south of this latitude. We used mitochondrial DNA (mtDNA) assays and wing geometric morphometrics to determine the prevalence of Africanized honey bees in managed populations. African mitotype origin and subspecies identity, were determined at three regions from Argentina. In our study, we analyzed 480 samples by wing morphometry and 157 by cytochrome-b assays, collected during 2013–2016. Our results show that North of 35°N latitude, honey bees with African mitotype were quite common (88.64%) finding high similarity with A. m. scutellata. South of that latitude, in temperate regions, we found African mitotype in only 18 of 133 colonies analyzed and a mixture of both European (A. m. ligustica, A. m. cárnica, A. m. mellifera) and African subspecies, most likely derived from North African honey bee (A. m. intermissa). Our results confirmed the existence of Africanized honey bee populations with a gradual cline from north to south, as a result from recent A. m. scutellata-derived bee expansion. Beyond the transition area between the 30°–35°S parallels bees carrying the European mitotype were fairly common.

1956年，非洲蜜蜂亚种东非蜜蜂（Apis mellifera scutellata）从巴西南部开始在美洲大陆扩散。非洲化过程涉及欧洲蜜蜂与非洲化蜜蜂之间双向的母系与父系基因交流。在阿根廷，非洲化蜜蜂在北部亚热带地区占据优势，且在约南纬32°–34°区域存在杂交带。尽管此前已在布宜诺斯艾利斯省开展过相关分析，但该纬度以南区域尚未有相关研究。本研究采用线粒体DNA（mtDNA）检测与翅膀几何形态测量法，以确定人工饲养蜂群中非洲化蜜蜂的占比。研究人员在阿根廷的三个区域对非洲线粒体单倍型起源及亚种归属进行了鉴定。本研究共分析了2013–2016年间采集的480份翅膀形态测量样本与157份细胞色素b检测样本。研究结果显示，在南纬35°以北区域，携带非洲线粒体单倍型的蜜蜂占比高达88.64%，且与东非蜜蜂的遗传相似度较高。在该纬度以南的温带区域，本次分析的133个蜂群中仅18个携带有非洲线粒体单倍型，且蜂群为欧洲蜜蜂与非洲蜜蜂的混合种群：欧洲蜜蜂亚种包括意大利蜜蜂（Apis mellifera ligustica）、卡尼鄂拉蜜蜂（Apis mellifera cárnica）与欧洲黑蜂（Apis mellifera mellifera），非洲亚种则大概率源自北非蜜蜂（Apis mellifera intermissa）。本研究结果证实，受近期东非蜜蜂扩散的影响，阿根廷境内的非洲化蜜蜂种群呈现出从北到南的渐变地理分布格局。在南纬30°–35°之间的过渡带以外区域，携带欧洲线粒体单倍型的蜜蜂较为常见。